List of index fossils

Index fossils (also known as guide fossils or indicator fossils) are fossils used to define and identify geologic periods (or faunal stages). Index fossils must have a short vertical range, wide geographic distribution and rapid evolutionary trends. Another term, "zone fossil", is used when the fossil has all the characters stated above except wide geographical distribution; thus, they correlate the surrounding rock to a biozone rather than a specific time period.

FossilScientific NameGeological time intervalMillion Years Ago

Calico scallop
Argopecten gibbus		Quaternary1.8 million years ago
Neptunea tabulataQuaternary1.8 million years ago
Viviparus glacialisTiglian (Early Pleistocene)0.5 million years ago
Calyptraphorus velatusTertiary
Venericardia planicostaEocene

Scaphites		Scaphites hippocrepisCretaceous145 to 66 million years ago

Inoceramus		Inoceramus labiatusCretaceous

Perisphinctes		Perisphinctes tizianiJurassic201.3 to 145 million years ago
Nerinea trinodosaJurassic
Tropites subbullatusTriassic
Monotis subcircularisTriassic

Leptodus		Leptodus americanusPermian
ParafusulinaParafusulina boseiPermian
Dictyoclostus americanusPennsylvanian
Lophophyllidium proliferumPennsylvanian
Cactocrinus multibrachiatusMississippian
Prolecanites gurleyiMississippian

Mucrospirifer		Mucrospirifer mucronatusDevonian416 to 359 million years ago
Palmatolepis unicornisDevonian
Tetragraptus fructicosusOrdovician
ParadoxidesCambrian509 to 500 million years ago
Billingsella corrugataCambrian
ArchaocyathidsCambrian529 to 509 million years ago
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See also

References
  1. Index Fossils, from the US Geological Survey. Updated July 31, 1997.
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